Traffic engineering concerns the optimization of whole network performance, and mainly aims to provide high-effective and reliable network services, to optimize the use of network resource, and to optimize network traffic. In particular, there are two aspects: one is traffic-oriented, i.e. to concern how to improve the quality of service in the network; the other is resource-oriented, i.e. to concern how to optimize the use of network resource, and mainly to optimize the effective utilization of bandwidth resource. As the deployment increases and General Multiprotocol Label Switching (GMPLS) develops, inter-domain traffic engineering will span different operators and cover the GMPLS network.
Constrained path computation, e.g. Constrained Shortest Path First (CSPF) computation is an important part of Multiprotocol Label Switching (MPLS) and GMPLS traffic engineering. Path computation among autonomous systems is complex, because computation entities within different autonomous systems should cooperate with each other to accomplish the path computation. A Path Computation Element (PCE) is a function entity, which can compute a path in accordance with a network topology architecture and constraint conditions. The PCE is compatible with the existing MPLS/GMPLS protocol and adaptable for operation mode of the existing MPLS/GMPLS network. The PCE, adopting a single signaling protocol and architecture, is adapted for different network environments, e.g. intra-domain, inter-domain and between different operators. The PCE allows operators or device manufactures to use different route algorithms, and compute routes in accordance with complex traffic engineering parameters and policies, thereby implementing a flexible system architecture. The PCE may be combined with a network element, or implemented in a separate server.
A PCE model-based path computation method may be adapted for inter-domain traffic engineering. The computation method does not affect the use of a computed path (the use of a computed path means, for example, establishment, maintenance and disconnection of a Label Switched Path (LSP)), but dedicates to computation of such an LSP.
Path Computation Client (PCC) refers to any client application which requests PCE for path information. In the PCE model-based path computation method, if a PCC such as an ingress Label Switching Router (LSR) which sends a path computation request desires to establish an LSP, the PCC first sends the PCE a request message including basic information such as path destination and various constraint conditions. The PCE receives the request, computes a path meeting the constraint conditions of the request in accordance with information such as Traffic Engineering Database (TED) and topology synchronized with the network, and returns the path to the PCC through a response message. The path is taken as an Explicit Route Object (ERO) parameter for establishing the LSP by the PCC. The computed path may include an explicit node (e.g. a router) and a loose node (e.g. a network segment, an area and an autonomous system).
In the PCE model-based path computation method, a computation made by each PCE usually covers an autonomous system. The autonomous system is particularly a range in which Traffic Engineering Database (TED) messages are distributed in an Interior Gateway Protocol (IGP).
In the PCE model, two basic protocols are required: PCE discovery protocol, responsible for PCC discovering the existence and computation ability of PCE, and selecting an appropriate PCE so as to send a path computation request to the selected PCE for computation in accordance with the information obtained from the protocol; and PCE communication protocol, mainly responsible for transporting path computation requests and response messages between PCCs and PCEs. The path computation requests from the PCCs contain various constraint conditions. If a PCE receives a path computation request which is specified to be processed locally, the PCE will perform a path computation accordingly.
At present, corresponding macro requirements are proposed for PCE communication. However, no corresponding solutions are proposed. The PCE communication protocol is being constituted.